Communication devices such as wireless devices may also be known as e.g. user equipments (UEs), mobile terminals, wireless terminals and/or mobile stations. A wireless device is enabled to communicate wirelessly in a cellular communication network, wireless communication system, or radio communication system, sometimes also referred to as a cellular radio system, cellular network or cellular communication system. The communication may be performed e.g. between two wireless devices, between a wireless device and a regular telephone and/or between a wireless device and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the cellular communication network. The wireless device may further be referred to as a mobile telephone, cellular telephone, laptop, Personal Digital Assistant (PDA), tablet computer, just to mention some further examples. The wireless device may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and/or data, via the RAN, with another entity, such as another wireless device or a server.
The cellular communication network covers a geographical area which is divided into cell areas, wherein each cell area is served by at least one base station, or Base Station (BS), e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. Cells may overlap so that several cells cover the same geographical area. By the base station serving a cell is meant that the radio coverage is provided such that one or more wireless devices located in the geographical area where the radio coverage is provided may be served by the base station. One base station may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the wireless device within range of the base stations.
In some RANs, several base stations may be connected, e.g. by landlines or microwave, to a radio network controller, e.g. a Radio Network Controller (RNC) in Universal Mobile Telecommunication System (UMTS), and/or to each other. The radio network controller, also sometimes termed a Base Station Controller (BSC) e.g. in GSM, may supervise and coordinate various activities of the plural base stations connected thereto. GSM is an abbreviation for Global System for Mobile Communication (originally: Groupe Special Mobile).
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs or eNBs, may be directly connected to other base stations and may be directly connected to one or more core networks.
UMTS is a third generation mobile communication system, which evolved from the GSM, and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for wireless devices. High Speed Packet Access (HSPA) is an amalgamation of two mobile telephony protocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), defined by 3GPP, that extends and improves the performance of existing 3rd generation mobile telecommunication networks utilizing the WCDMA. Moreover, the 3GPP has undertaken to evolve further the UTRAN and GSM based radio access network technologies, for example into evolved UTRAN (E-UTRAN) used in LTE.
The expression downlink (DL) is used for the transmission path from the base station to the wireless device. The expression uplink (UL) is used for the transmission path in the opposite direction i.e. from the wireless device to the base station.
In LTE-based wireless communication systems, a downlink Paging Control Channel (PCCH) may be used to transmit paging information via one or more eNBs serving one or more cells in which the UEs may be located. Paging may e.g. be used to notify UEs of changes in System Information (SI) which will require a reacquisition of SI. The paging channel may also be used to notify the UEs of the presence of Earthquake and Tsunami Warning System (EWTS) information. The paging channel may be used to communicate with a UE when the wireless communication system does not know the exact location and/or cell of the UE and/or when the UE e.g. is in idle mode. In idle mode the UEs may use Discontinuous Receive (DRx) to e.g. reduce battery life. DRX may be configured via parameters to monitor the Physical Downlink Control Channel (PDCCH) channel at regular intervals, set by DRx parameters, in order to check for the presence of a paging message. If the PDCCH indicates that a paging message is transmitted in a subframe the UE may demodulate a paging channel (PCH) to see if there is a paging message directed to it.
Further, paging messages may be sent to all or a subset of eNBs in a Tracking Area (TA) and/or in TAs that are entered in a TA list. These paging messages may e.g be sent from or via a Mobility Management Entity (MME) and may be termed S1 Application Protocol (S1-AP) paging messages. In response to receipt of such paging message, or separate therefrom, an eNB may transmit another paging message, that may be termed Radio Resource Control (RRC) paging message. This paging message will thus be transmitted in a cell that the eNB serves and in which one or many UEs targeted by the RRC paging message may be located.
In short, in LTE, a paging, or page, procedure may be used by the core network to trigger a UE to connect to the network and thus become available to take a call or receive data. For this purpose an S1-AP paging message may be sent from the MME to an eNB. The eNB in turn uses the information in the S1-AP message to create a Radio Resource Control (RRC) paging message, which is transmitted in one or more cells served by the eNB.
Paging in LTE is e.g. described in:
3GPP TS 36.304 that describes a UE procedure for paging reception, see e.g. v.11.6.9, chapter 7.
3GPP TS 36.331 that describes the RRC part of the paging message, see e.g. v.11.9.0, chapter 6.2.2. 3GPP TS 36.413 that describes the S1-AP procedure and message, see e.g. v.11.6.0, chapter 8.5 and 9.1.6.
In general, paging in a wireless communication network is about a functionality that enables the network to trigger a wireless device to connect to the wireless communication network when the wireless device is in an idle or sleep mode.
For some DL transmissions in LTE, e.g. in the case of transmitting paging messages to UEs, it is hard to estimate the corresponding DL channel as an eNB may have no idea if the UE is located in a cell that the eNB serves, or if it is not. Basically, nothing may be known about the link conditions between the eNB and UE. Yet the paging message should be sent to the UE. In order to maximize or at least increase the chance for the paging message to reach the UE successfully, the eNB may assume that the UE is located in a spot with very poor coverage, i.e. that the UE experiences a very poor channel. This is a robust solution, but wastes radio resources since this situation is typically not the case for most UEs.
With existing solutions for LTE, there is no way for the eNB to know about link conditions to the UE. Thus, a very robust coding and/or high transmit power may be used in order to guarantee that also UEs at the cell-edge are reached. If a less robust coding and/or lower transmit power instead was chosen, then such UEs would effectively be in a coverage-hole and not reachable by the wireless communication system.
A problem with this approach is that, in many cases, a too robust coding is chosen. In many cases the UEs are not at the cell-edge, but rather experience medium or even good radio conditions. When such UEs receive a page it is clear that resources are wasted, primarily PDCCH and Physical Downlink Shared Channel (PDSCH) resources.